• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2001년도 제33회 춘계학술대회 개최
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• pp.265-270
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• 2001

Hip joint simulator which Is an essential device for evaluating the wear of biomaterials (ultrahigh molecular weight polyethylene, Co-Cr alloy, alumina, etc.) used in total hip joint replacement was developed. This hip joint simulator mimics the joint motion and joint loading of human gait by adapting the 4 degree of freedom in kinematic motion (flexing/extension, adduction/abduction, Internal rotation/external rotation) and axial loading, Four stations are operated by 8 servo-motors and harmony drives. Joint leading was imposed by displacement control from a ball screw, LM guide, and spring system. Each kinematic link system operates separately or coupled modes. A heater and a thermocouple were installed for keeping the body temperature in each station.

• Interaction and multiscale mechanics
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• 제4권1호
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• pp.1-16
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• 2011

The inverse problem about the theoretical analysis of a drill string bending in a channel of an inclined bore-hole with localized geometrical imperfections is studied. The system of ordinary differential equations is first derived based on the theory of curvilinear flexible elastic rods. One can then use these equations to investigate the quasi-static effects of the drill string bending that may occur in the process of raising, lowering and rotation of the string inside the bore-hole. The method for numerical solution of the constructed equations is described. With the proposed method, the phenomenon of the drill column movement, its contact interaction with the bore-hole surface, and the frictional seizure can be simulated for different combinations of velocities, directions of rotation and axial motion of the string. Geometrical imperfections in the shape of localized smoothed breaks of the bore-hole axis line are considered. Some numerical examples are presented to illustrate the applicability of the method proposed.

• 설비공학논문집
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• 제18권4호
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• pp.370-376
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• 2006

The paper concerns an experimental study of fully developed laminar flow of a Newtonian and non-Newtonian liquid in concentric annuli with combined bulk axial flow and inner cylinder rotation. Pressure losses and skin friction coefficients have been measured for Newtonian fluid, water and non-Newtonian fluids, 0.2% aqueous of sodium carboxymethyl cellulose (CMC) and 5% bentonite solutions, when the inner cylinder rotates at the speed of $0{\sim}500$ rpm. The influences of rotation, radius ratio and working fluid on the annular flow field are investigated. And the new correlations among the skin friction coefficient, the Reynolds number and the Rossby number are presented with reasonable limits of accuracy in laminar flow regime.

• 한국공간구조학회논문집
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• 제23권3호
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• pp.45-55
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• 2023

The purpose of this study has a purpose to evaluate shear ability, ductility and energy dissertation of specimens that is to be applied to jacket using wrapping method. The experiments was conducted as a condition that simultaneously applied axial load and transverse force. The results of experiments represent story-displacement ratio, the stiffness, energy dissertation, plastic rotation which mean seismic resistance ablity on structure. And It represents the form of crack ditribution and failure in extreme stages. Based on the results of this experiment, Design examples are given to show the performance evaluation for the column reinforcing of old school buildings using nonlinear analysis is going to be conducted. Therefore, it is possible to apply the seismic retrofit method to public facilities.

• 한국전자파학회논문지
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• 제18권2호
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• pp.158-165
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• 2007

본 논문은 X-band에서 동작하는 마이크로스트립 원형 편파 $4{\times}4$ 배열 안테나의 설계와 제작에 대해 다룬다. 단일 안테나는 정사각형 패치를 사용하고 비대칭 십자 개구 결합 급전 구조를 사용하여 RHCP(Right Handed Crcularly Polarization)로 동작하도록 하였다. 기존의 배열 안테나의 소자간의 간격을 0.8 ${\lambda}_0$에서 0.45 ${\lambda}_0$로 간격을 줄여 실장 면적을 감소시켰다. 급전 선로는 시퀀셜 로테이션 분배기로 $2{\times}2$ 배열 안테나를 설계하여 양호한 이득과 축비 대역폭을 나타내었다 ${\lambda}/4$ Transformer와 T-junction 전력 분배기로 $4{\times}4$ 배열 안테나로 확장하였다. 시뮬레이션으로 확인한 결과 최대 방사 이득은 15.09 dBi로 나타났으며, 축비 대역폭은 3 dB 기준 $9.05{\sim}10.4$ GHz(13.5%)의 양호한 특성을 보였다. 제작된 $4{\times}4$배열 안테나는 10 GHz에서 측정 결과 임피던스 대역폭($VSWR{\leq}2$)은 $8.45{\sim}11.84$ GHz(33.9%)로 나타났으며, 최대방사 이득은 11.10 dBi를 얻었다. 또한 측정된 축비 대역폭은 $9.42{\sim}10.47$ GHz(10.5%)를 얻었다.

• Computers and Concrete
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• 제7권4호
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• pp.303-315
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• 2010

In this paper, we present a new finite Timoshenko beam element with a model for ultimate load computation of reinforced concrete frames. The proposed model combines the descriptions of the diffuse plastic failure in the beam-column followed by the creation of plastic hinges due to the failure or collapse of the concrete and or the re-bars. A modified multi-scale analysis is performed in order to identify the parameters for stress-resultant-based macro model, which is used to described the behavior of the Timoshenko beam element. The micro-scale is described by using the multi-fiber elements with embedded strain discontinuities in mode 1, which would typically be triggered by bending failure mode. A special attention is paid to the influence of the axial force on the bending moment - rotation response, especially for the columns behavior computation.

• Progress in Superconductivity
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• 제3권2호
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• pp.178-182
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• 2002

Superconducting four-element patch array antenna was designed and fabricated using $high-T_{c}$ superconducting (HTS) thin film. The array antenna has single-feed circularly polarization and a resonance frequency of 11.85 GHz fur satellite communication system. To fabricate this antenna $YBa_2$$Cu_3$$O_{7-x}$(YBCO) superconducting thin films were deposited using rf-magnetron sputtering technique. Sequential rotation technique based on radiation elements($0^{\circ}$ , $90^{\circ}$, 1$80^{\circ}$, $270^{\circ}$ phase delay) was utilized to achieve circularly polarization. Simulated and measured results, the analysis on resonant frequency(fr), return loss, and bandwidth are presented. The results show that 10 dB return loss bandwidth of the array antenna is 11.04 GHz~12.59 GHz (13.15%) and 3dB axial ratio bandwidth is 11.42~12.52 GHz (9.2%).).).

• Structural Engineering and Mechanics
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• 제43권2호
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• pp.147-161
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• 2012

This paper presents a curvature method for analysis of beam-columns with different materials and arbitrary cross-section shapes and subjected to combined biaxial moments and axial load. Both material and geometric nonlinearities (the p-delta effect in this case) were incorporated. The proposed method considers biaxial curvatures and uniform normal strains of discrete cross-sections of beam-columns as basic unknowns, and seeks for a solution of the column deflection curve that satisfies force equilibrium conditions. A piecewise representation of the beam-column deflection curve is constructed based on the curvatures and angles of rotation of the segmented cross-sections. The resulting bending moments were evaluated based on the deformed column shape and the axial load. The moment curvature relationship and the beam-column deflection calculation are presented in matrix form and the Newton-Raphson method is employed to ensure fast and stable convergence. Comparison with results of analytic solutions and eccentric compression tests of wood beam-columns implies that this method is reliable and effective for beam-columns subjected to eccentric compression load, lateral bracings and complex boundary conditions.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2002년도 춘계종합학술대회
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• pp.234-237
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• 2002

Sierpinski 프랙탈 삼각형을 이용한 원형 편파를 가지는 마이크로스트립 패치 안테나를 제안한다. Sierpinski 프랙탈 삼각형은 3개의 정삼각형을 가지는 구조로 이를 이용하여 sequential 회전에 의해 원형 편파를 발생시킬 수 있다. Sierpinski 구조의 $1\times3$ 안테나 배열에 대해 포트간 분리도(isolation) 와 AR(Axial Ratio)의 특성을 살펴보았다.

• Structural Engineering and Mechanics
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• 제17권6호
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• pp.829-862
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• 2004

This paper presents a method for the nonlinear analysis of beam elements subjected to the cyclical combined actions of torsion, biaxial flexure and axial forces based on an extension of the disturbed compression field (DSFM). The theoretical model is based on a hybrid formulation between the full rotation of the cracks model and the fixed direction of the cracking model. The described formulation, which treats cracked concrete as an orthotropic material, includes a new approach for the evaluation of the re-orientation of both the compression field and the deformation field by removing the restriction of their coincidence. A new equation of congruence permits evaluating the deformation of the middle line. The problem consists in the solution of coupled nonlinear simultaneous equations expressing equilibrium, congruence and the constitutive laws. The proposed method makes it possible to determine the deformations of the beam element according to the external stresses applied.